Simulated decorative transfer films and foils are used for providing a decorative pattern, for example, the appearance of real wood grain, to many substrates including furniture, countertops, walls, siding and automobiles. The typical method for applying such films and foils to a substrate includes use of a pressure-sensitive adhesive. However, such adhesives are sensitive with respect to placement and, if not positioned accurately, provide a poor fit and an irregular surface.
Heat-activatable adhesives have been used as substitutes for pressure-sensitive adhesives. However, in many instances, little or no adhesion is achieved between the substrate and the transfer layer. Further, in order to activate the adhesive, the film must be heated to a temperature in excess of the softening temperature of the film or foil thereby resulting in distortion or loss of the three-dimensional design or in shrinkage of the carrier sheet supporting the foil which also causes distortion. Such adhesive layers are generally applied by roller application using a solvent based system which includes the adhesive as a solid component in the solution. The solvent must then be volatilized leaving the adhesive layer on the film.
Further, such adhesive formulations include a large amount of solvent and contribute substantially to the overall amount of solvent used to form the films. High quantities of solvent pose environmental and manufacturing problems. In addition to the potential environmental and health hazards which result from solvent use, and the expense of disposal and environmental compliance, solvent-based coatings also increase manufacturing cost due to long drying times necessary for solvent evaporation. Substitution of water-based coatings which may reduce environmental concerns, still require long drying times. Further, such coatings exhibit poor rheological properties which manifest as orange peeling and non-uniform film thickness. Therefore, there is a need in the art for a solvent-free adhesive system which would reduce the overall amount of solvent used in manufacture of decorative films and eliminate oven drying time and which also provides a uniform and smooth film.
There is a need in the art for a uniform, easy-to-apply, solvent-free, heat-activatable adhesive layer which can be activated without harming the design layer of the decorative foil or film, which reduces the environmental impact resulting from the use of solvents and which eliminates oven drying time. There is also a need in the art for a method of applying a heat-activatable adhesive layer to a decorative foil or film which does not harm the decorative design, which does not shrink the carrier sheet supporting the decorative layers which would otherwise cause distortion, which sets quickly without use of oven drying and allows for a uniform, permanently bonded foil upon application to the substrate.